WHAT IS A HIGH-FLOW NASAL CANNULA (HFNC)?
A high-flow nasal cannula (HFNC) is a heated and humidified system that allows prescribed fraction of inspired oxygen (FIO2) levels to be delivered at very high flow rates. The main intended use of HFNC: precise oxygen delivery, improve gas exchange, significantly reduce the work of breathing, and create a reservoir with high FIO2 in the nasal cavity.
Let’s now consider how HFNC can help patients improve their respiratory disease.
HOW DOES HIGH FLOW NASAL CANNULA WORK?
HFNC is carried out using an air/oxygen blender, active humidifier, single heated tube, and nasal cannula. HFNC can warm (to 98.6oF or 37oC) and humidify gas, which can decrease airway inflammation, maintain mucociliary function, improve mucous clearance and reduce the caloric expenditure in acute respiratory failure.
Additionally, a (HFNC) is able to deliver adequately heated and humidified medical gas at flows up to 60 L/min, HFNC like the Fisher and Paykel Airvo 2 is considered to have a number of physiological advantages compared with other standard oxygen therapies.
PRECISE OXYGEN DELIVERY
Traditional nasal cannula delivers flow rates of 2–6 L / min. However, patients with respiratory distress can have much higher peak inspiratory flow rates which can cause the patient to entrain room air into the lungs. This can result into an oxygen dilution, and the patient will not receive the precise amount of oxygen that is desired.
When high-flow nasal cannula is used to deliver oxygen, the flow rates are much higher than can be achieved with traditional nasal cannula. This results in a greater delivery of prescribed oxygen into the lungs, and less entrainment of room air.
DEAD SPACE WASHOUT
Lastly, when HFNC is applied, the constant high flow of oxygen provides a washout of the anatomical dead space of the oropharynx and proximal tracheobronchial tree, which results in more efficient breathing.
PUTTING HIGH-FLOW NASAL CANNULA (HFNC) TO USE
The main adult indications include hypoxemic respiratory failure due to pneumonia, post-extubation, pre-oxygenation prior to intubation, acute pulmonary edema, and use in patients who are “do not resuscitate or intubate”. The main pediatric indication in infants is bronchiolitis, but other indications are being studied, such as its use in asthma, croup, pneumonia, transport of a critically ill child, and post-extubation.
INTRODUCTION TO THE FISHER AND PAYKEL AIRVO 2
A perfect example of a high flow system is the Fisher and Paykel Airvo 2. This humidifier has an integrated flow generator that delivers high flow warmed humidified respiratory gases to spontaneously breathing patients through a variety of patient interfaces. The Airvo 2 is suitable for hospitals and long-term care facilities.
- Dual spiral heated breathing tube with an integrated temperature sensor.
- Use with Optiflow nasal cannula interfaces, direct-connect tracheotomy, and mask interfaces.
- Oxygen from a concentrator or cylinder optionally added.
- Built-in ultrasonic analyzer requires no calibration, service, or replacement.
- Adjustable temperature and flow settings.
- Designed for simple setup, use, and cleaning.
FISHER AND PAYKEL AIRVO 2 SPECIFICATIONS
- Height: 11.6” (29.5 cm)
- Width: 6.7” (17 cm)
- Depth: 6.9” (17.5 cm)
- Weight: 4.8 lbs (2.2 kg)
- Supply frequency: 50-60 Hz
- Supply voltage/current: 100-115 V 2.2 A (2.4 A max†); 220-240 V 1.8 A (2.0 A max)
- Sound pressure level: Alarms exceed 45dbA @ 1 m
- Auditory alarm pause: 115 seconds
- Expected service life: 5 years
- Serial port: The serial port is used for downloading product data, using F&P Infosmart software.
- Warm-up time: 10 minutes to 31 °C (88 °F), 30 minutes to 37 °C (98.6 °F) using a
- MR290 chamber with flow rate of 35 L/min and starting temperature 23 ± 2 °C (73 ± 3 °F)
- Target temperature settings: 37, 34, 31 °C
- Humidity performance
- >33 mg/L at 37 °C target
- >12 mg/L at 34 °C target
- >12 mg/L at 31 °C target
- Maximum temperature of delivered gas: 43 °C (109 °F) (in accordance with ISO 80601-2-74)
- Maximum surface temperature of applied parts: 44 °C (111 °F) (in accordance with ISO 80601-2-74)
- Flow range (default): 10-60 L/min
- Flow range (Junior Mode): 2-25 L/min
- Maximum oxygen input: 60 L/min
- Oxygen analyzer accuracy: < ± 4 % (within the range 25-95% O2)
- Operating conditions: 18-28 °C (64-82 °F), 30-70% RH
Physicians have been using it for a wide variety of underlying diseases and conditions. HFNC oxygen delivery has already proved its value as an effective mode of noninvasive ventilatory support and has been gaining attention as a simple and well-tolerated alternative means of respiratory support for critically ill patients.